JPS6156956B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel flow velocity and humidity simultaneous measurement device that can simultaneously measure the flow velocity of a gas, such as wind velocity, and the humidity of the gas.

Many devices have already been proposed that individually measure the flow velocity and humidity of gas and the like.

However, no method has been proposed in which both flow velocity and humidity can be measured at the same time using a single detection element.

The present invention has been proposed based on a novel technical idea, and is an extremely effective flow velocity and humidity simultaneous measuring device that can simultaneously measure the flow velocity of gas and its humidity. I will explain.

FIG. 1 is a partially cutaway schematic diagram of the detection element S, in which 1 indicates a resistance wire, for example, a fine wire made of a metal with a relatively large temperature coefficient of resistance, such as platinum, and the wire diameter is, for example, 20 to 50 μmφ. It is of a certain degree. 2 is a heat-resistant insulating material that covers the resistance wire 1. Reference numeral 4 denotes a porous metal oxide moisture resistor formed by sintering the resistance wire and its covering material as a core, and terminals 3a and 3b are embedded at both ends thereof, for example. 1a and 1b indicate terminals of the resistance wire 1.

It is assumed that the humidity sensitive resistor 4 is thermally coupled to the resistance wire 1 and always maintains a predetermined temperature, which will be described later.

In the detection element S having such a configuration, the resistance value between the terminals 3a and 3b decreases when the moisture-sensitive resistor 4 absorbs moisture.

A typical example of its humidity-resistance characteristics is shown in Figure 2.
FIG. 3 illustrates a specific circuit of the embodiment.
The above-mentioned detailed detection element S is a part delineated by a dotted line, and the resistance line 1 is shown replaced by a resistance R1, and the moisture-sensitive resistor 4 is replaced by a resistance 4'. .

The resistor R1 and the fixed resistors R2, R3,
A bridge circuit is constituted by R4, and potential changes at points a and b are input to an amplifying circuit 5, and from its output, a current I is fed back to the bridge circuit so that the bridge circuit maintains balance.

On the other hand, both terminals of the resistor 4', which changes depending on the humidity, are connected to a resistance value detection circuit 6, and the humidity display 7 displays the value of the resistor 4'.

Note that 8 is a flow rate indicator that displays a flow rate value as described later.

The resistance values on each side of the bridge are approximately R2 = 224Ω, R3 = 200Ω, and R4 = 20Ω, and the value of R1 is 22.4Ω from equation (2) described later. Note that the resistance temperature coefficient α of the resistor R1 is approximately 0.004.

In such a configuration, the resistance R at 0°C
If the resistance value of 1 is R0, its temperature coefficient of resistance is α, and its temperature is T, then R1=R0(1+αT) (1) holds true.

Also, the equilibrium condition of the bridge composed of resistors R1, R2, R3, and R4 is R1・R3=R2・R4 (2), and now resistor R1 is not heated and its resistance value is low. <R2·R4 (3) If so, the potential at point a in FIG. 3 becomes lower than point b.

Since the inverting input terminal of the amplifier 5 is connected to point a, and the non-inverting input terminal is connected to point b, when the potential at point a decreases, the output current I of the amplifier 5 increases, Resistor R1 will be heated.
Conversely, if the resistor R1 is heated too much, R1.R3>R2.R4 (4), and in this case, the potential at point a becomes higher than point b, and the current I decreases.

Through this operation, the bridge equilibrium condition, equation (2), is automatically satisfied, and the resistance value of R1 becomes constant. As a result, as shown by equation (1), the temperature of the resistor R1 is kept constant. Furthermore, R
0=20Ω.

Assuming that the resistance values on each side of the bridge are the values described above, the temperature of the resistor R1 at this time will be 30° C. from equation (1).

That is, in the embodiment, since the resistor R1 and the humidity sensitive resistor 4' are thermally coupled, the temperature of the resistor 4' is always maintained at 30°C.

Next, regarding humidity, the saturated pressure of water is 17.53 mmHg at a zero ambient temperature of 20°C, and becomes 31.83mmHg at 30°C. Relative humidity is the ratio of the water vapor pressure in a gas to the saturated water vapor pressure at the same temperature as the gas, expressed as a percentage.

Therefore, in the case of the embodiment, even if the ambient temperature is 20°C and the relative humidity is 100%, the temperature of the humidity-sensitive resistor 4' is maintained at 30°C as described above, so the resistor 4' itself Equivalently, 17.53/31.83×100=55.07 (5) That is, it corresponds to being in an atmosphere with a humidity of approximately 55%.

As can be seen from the characteristic diagram in Figure 2, this allows humidity to be detected within a range where the linearity of the humidity-resistance characteristics is good, thereby providing high measurement accuracy. .

Next, the operation of measuring the flow velocity will be explained. When the circuit of the embodiment operates as described above, equation (2) is satisfied, and therefore the value of the resistor R1 becomes constant. Note that the circuit constants of the resistor R1 are selected so that the resistor R1 remains constant at a temperature that is always higher than the ambient temperature.

The current to the resistor R1, ie the current I supplied to the bridge, is controlled so that the resistor R1 is at a constant temperature, and the heat generated by said current is dissipated into the surrounding gas. When the gas around the resistor R1 (more precisely, the gas passing through the moisture-sensitive resistor) is flowing, that is, when the gas is moving at a certain speed, the amount of heat dissipated increases, and therefore the current I also increases.

When the flow rate increases, the amount of heat dissipated from the resistor R1 increases and thus the resistor R1 is cooled. When cooled, its resistance value decreases, resulting in equation (3).

In such a state, the current I increases due to the operation of the circuit.
increases, and the resistor R1 is heated. Then again (2)
The condition of Eq.

When the flow rate decreases, the amount of heat dissipated from resistor R1 decreases, and therefore the temperature of the resistor increases. As it rises, its resistance value becomes high, so the current I decreases and the temperature of the resistor R1 decreases, as shown in equation (4).
Equation (2) is satisfied again.

When the flow velocity changes in this way, the current I changes accordingly. In the embodiment, a signal corresponding to this current change is extracted to drive the flow rate indicator 8,
The flow velocity value can be determined from the indicated value. In the above explanation, the humidity measurement operation and the flow rate measurement operation were explained separately, but in reality, these are performed at the same time, and the humidity indicator 7 and the flow rate indicator 8 are used to measure the gas to be measured. It is possible to measure the humidity and flow velocity of the air at the same time.

As described in detail above, the present invention, despite its relatively simple structure, can simultaneously perform two measurements of humidity and flow rate, and has extremely great effects in use.
Furthermore, in the embodiment, since the humidity-sensitive resistor is always heated to a constant temperature, the drying operation of the humidity-sensitive resistor during long-term high-humidity measurements is less than that required in the conventional method. The present invention has excellent effects in this respect as well.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway cross-sectional view showing an example of a detection element used in a simultaneous flow velocity and humidity measuring device according to an embodiment of the present invention, and FIG. 2 is a graph showing changes in resistance value of this detection element with respect to humidity. FIG. 3 is a circuit diagram showing the configuration of a simultaneous flow rate and humidity measuring device according to an embodiment of the present invention. S...Detection element, 1...Resistance wire, 1a, 1b...Terminal, 2...Heat-resistant insulating material, 3a, 3b...Terminal, 4...Moisture-sensitive resistor, R1, R2, R3, R4, r...Resistance,
4'...Humidity sensitive resistor, 5...Amplifier, 6...Resistance value detection circuit, 7...Humidity indicator, 8...Flow rate indicator.

Claims (1)

[Scope of Claims] 1. A detection element configured by wrapping and thermally coupling a coated resistance wire having a resistance value depending on temperature with a moisture sensitive body, and providing terminals at both ends of the moisture sensitive body; a bridge circuit having a resistance wire in a detection element on one side; a feedback amplifier having a pair of terminals of the bridge circuit connected to an input terminal and keeping the bridge in balance by supplying a feedback current to the bridge circuit; and the feedback amplifier. a flow velocity indicator that displays the flow velocity corresponding to the feedback output of the bridge; a resistance value detection circuit that detects the resistance value of the moisture sensitive body maintained at a predetermined temperature by the equilibrium of the bridge; and a resistance value of the resistance value detection circuit. A flow rate and humidity simultaneous measuring device comprising: a humidity indicator that displays the humidity around the humidity sensitive resistor by output. 2. Simultaneous measurement of flow velocity and humidity according to claim 1, wherein the detection element is formed by sintering a porous moisture material around a coated resistance wire as a core. Device. 3. The flow velocity and humidity simultaneous measuring device according to claim 1, wherein the resistance wire of the humidity-sensitive resistor is a metal wire having a large temperature resistance coefficient. 4. The flow rate and humidity simultaneous measuring device according to claim 3, wherein the resistance wire is a platinum wire.